One-pot synthesis of Pd20-xAux nanoparticles embedded in nitrogen doped graphene as high-performance electrocatalyst toward methanol oxidation

• Published in: International journal of hydrogen energy 2020-01, Vol.45 (1), p.1018-1029
• Main Authors: Sunil Kumar, V., Kummari, Shekher, Yugender Goud, K., Satyanarayana, M., Vengatajalabathy Gobi, K.
• Format: Article
• Language: English
• Subjects: Electrocatalysis; Methanol oxidation; N-doped graphene; Pd nanoparticles; PdAu bimetallic nanoparticles
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2019.10.197

Mixed Pd–Au bimetallic nanoparticles embedded nitrogen doped graphene composites (PdAu/NG180) are explored for efficient electrocatalytic oxidation of methanol. A simple hydrothermal one-pot polyol method, involving simultaneous reduction of both Pd and Au, is utilized for the synthesis of Pd20-xAux/NG180 (x wt % = 0, 5, 10 and 15). This method is of multiple advantages such as inexpensiveness, reagent-free and environment-friendly being surfactant free. The morphology, crystal structure and chemical composition of NG180, Pd/NG180 and Pd20-xAux/NG180 catalysts are analyzed by XRD, FESEM-EDX, TEM, XPS and Raman spectroscopy methods. Electrocatalytic activities of PdAu/NG180 nanocomposites toward methanol oxidation reaction (MOR) in alkaline media are investigated by cyclic voltammetry, chronoamperometry and CO stripping measurements. Pd20-xAux/NG180 exhibited an increase in the electroactive surface area of Pd to twice by the coexistence of Au. In cyclic voltammetry studies, Pd10Au10/NG180 catalyst exhibits highest peak current density for MOR and is 1.5 times highly efficient compared to Pd20/NG180 with an enhanced shift in the onset potential by 140 mV to lower overpotentials. Besides, Pd10Au10/NG180 catalyst exhibited enhanced electroactive surface area and long-time durability in comparison to Pd20/NG180 catalyst. The steady state current density for MOR observed with Pd10Au10/NG180 at the end of 4000 s (98 mA mg−1Pd) is higher than those observed with all the other catalysts at the end of mere 1000 s alone (97, 61, and 32 mA mg−1Pd). The promising high electrocatalytic activity of Pd10Au10/NG180 is well corroborated from CO stripping experiments that the specific adsorption of CO onto Pd10Au10/NG180 (0.71 C m−2) is merely half to that observed onto Pd20/NG180 (1.49 C m−2). [Display omitted] •NG180 promotes electronic interaction and fine dispersion of metallic nanoparticles.•One-pot polyol method employed for simultaneous reduction of Pd and Au.•Co-existence of Au exhibited higher electrocatalytic activity toward MOR.•Pd20-xAux/NG180 exhibited higher mass current density and durability toward MOR.